Potentiometer Signal Too High

B A. Diagnostic trouble code (DTC) information





Condition
Motor 2 controls the backrest angle. If the voltage from the potentiometer for motor 2 to control module terminal V2 exceeds 4.6 V diagnostic trouble code (DTC) PSL/PSR-121 is set.

Possible source
- Contact resistance in terminals.
- Loose contacts in terminals.
- Defective potentiometer, motor 2.
- Open-circuit in ground lead between control module and potentiometer, motor 2.
- Signal wire between control module and potentiometer for motor 2 short-circuited to battery voltage.
- Supply wire between control module and potentiometer for motor 2 short-circuited to battery voltage.
- Defective control module.

Fault symptom(s)
- Memory activation does not work.
- Fault-tracing begins at BB. Potentiometer signal too high.

B B. Potentiometer signal too high





BB1: Checking status
- Ignition OFF.
Select scrolling values and read off the value from the potentiometer for motor 2.

Adjust the backrest forward and backward between the end positions several times using the control button.

The potentiometer value must not exceed 4.6 V at any time.

If reading is OK:
- BB13

If reading is incorrect:
- BB2








BB2: Checking resistance in circuit to potentiometer
- Ignition OFF.
- Remove seat from car.
- Disconnect gray 14-pin connector B.
Connect an ohmmeter between positions B:4 and B:5 on gray 14-pin connector (potentiometer side).

The ohmmeter should read approx. 2200 ohm.

If reading is OK:
- BB8

If reading is incorrect:
- BB3





BB3: Checking potentiometer resistance
- Ignition OFF.
- Disconnect the gray 14-pin connector.
- Remove potentiometer on motor 2.
Connect an ohmmeter between two outer terminals on the potentiometer.

The ohmmeter should read approx. 2200 ohm.

If reading is OK:
- BB5

If reading is incorrect:
- BB4

BB4: Replace component
Test with new potentiometer. Motor and potentiometer in backrest, Service and Repair

Then continue with:
- BB11





BB5: Checking potentiometer's ground
- Ignition OFF.
- Disconnect 3-pin connector to potentiometer on motor 2.
- Disconnect the gray 14-pin connector B.
Connect an ohmmeter between the gray 14-pin connector position B:4 and the corresponding position on the 3-pin connector (yellow-white lead).

The ohmmeter should read approx. 0 ohm.

If reading is OK:
- BB7

If reading is incorrect:
- BB6





BB6: Checking for an open-circuit
Check the yellow/white ground lead between the control module, position B:4, and the potentiometer for open circuit.

Then continue with:
- BB11





BB7: Checking, contact resistance and oxidation
Check the 3-pin connector to the potentiometer on motor 2 for contact resistance and oxidation and take corrective action.

Then continue with:
- BB11





BB8: Checking the supply and signal leads on the potentiometer
- Ignition OFF.
- Disconnect the gray 14-pin connector B.
Connect an ohmmeter between supply lead, terminal B:5, and the two supply leads to the motor, terminals B:1-B:2, in the gray 14-pin connector on the potentiometer side.

Connect an ohmmeter between signal lead, terminal 8:3, and the two supply leads to the motor, terminals B:1-B:2, in the gray 14-pin connector on the potentiometer side.

The ohmmeter should read infinite resistance for all readings.

If reading is OK:
- BB10

If reading is incorrect:
- BB9





BB9: Checking for a short-circuit
The measurements show that the signal lead or supply lead to the potentiometer is short-circuited to battery voltage.

Check the blue/white supply lead between position 8:5, and the potentiometer on motor 2 for short-circuit to supply.

Check the white signal lead between position 8:3, and the potentiometer on motor 2 for short-circuit to supply.

Then continue with:
- BB11





BB10: Checking control module and connector B
Potentiometer and cables are fault-free

Check and correct the 14-pin gray connector B for contact resistance and oxidation. Checking wiring and connections, Component Tests and General Diagnostics

If the fault persists after verification, try a new control module, Service and Repair

Then continue with:
- BB11





BB11: Verification
Hint: After carrying out the repair, check that the fault has been remedied as follows:
- Ignition OFF.
- Reinstall components, connectors etc.
- Connect up seat in car.

Select scrolling values and read off the value from the potentiometer for motor 2.

Operate the backrest forward/backward, running it to the stop positions in both directions.

The values indicated for potentiometer 2 must not be more than 4.6 V or less than 0.2 V.

If reading is OK:
- Fault corrected

If reading is incorrect:
- BB12

BB12: Fault-tracing information
The verification result shows that the fault persists.
Do you want to exit fault-tracing?

Yes:
- Fault not corrected

No:
- BB1








BB13: Intermittent fault
Check the gray 14-pin connector B and potentiometer connector to motor 2 for loose contacts and contact resistance and oxidation.

Check the ground lead between control module, terminal B:4 (yellow white lead), and the potentiometer on motor 2 for intermittent open-circuit.

Control the signal and supply leads between the control module and the potentiometer on motor 2, terminal B:3 and and:5, for intermittent short-circuit to supply.

Then continue with:
- BB14

BB14: Fault-tracing information
For intermittent faults fault-tracing is not followed by a verification because the fault is not present at this moment.
Do you want to repeat fault-tracing?

Yes:
- BB1
No:
- Operation done